Hub-to-shaft clamp connection assembly

ABSTRACT

To connect a hub to a shaft, spaced inner and outer rings have conical surfaces formed thereon, the conical surfaces diverging towards the outer sides of the connection. A pair of intermediate clamp rings which have essentially matching (but possibly slightly smaller conical angles) conical surfaces are inserted between the inner and outer rings, one from each side. Screws pass through one of the clamp rings and bear against its outer face, and are threaded into the other clamp ring, to tighten the rings against each other, the inner and outer rings being formed with a central recess of dove-tailed cross-section, in which a ring-shaped metal disc is inserted having an outer surface substantially matching the dove-tailed conical surfaces of the inner and outer rings. The clamp ring against which the screw surfaces bear is additionally formed with threaded openings to permit screws to be threaded therein, to then bear against the metal ring when separation of the hub to shaft connection is desired.

United States Patent Peter et al.

[151 3,679,247 51 July 25,1972

[541 HUB-TO-SHAFT CLAMP CONNECTION ASSEMBLY [72] Inventors: Oskar E.Peter, Schlosstrasse, 9/1, 7129 Brackenheim; Lothar Peter, Wagnerstrasse8, 7129 Guglingen, both of Germany [73] Assignee: said Oskar E. Peter,by said Lothar Peter [22] Filed: Oct. 26, 1971 21 Appl. No.: 191,994

525,775 9/1894 Wainwright ..287/52.06

,QTHEB PQBHCATIQES Primary Examiner-Andrew V. Kundrat [5 7] ABSTRACT Toconnect a hub to a shaft, spaced inner and outer rings have conicalsurfaces formed thereon, the conical surfaces diverging towards theouter sides of the connection. A pair of intermediate clamp rings whichhave essentially matching (but possibly slightly smaller conical angles)conical surfaces are inserted between the inner and outer rings, onefrom each side. Screws pass through one of the clamp rings and bearagainst its outer face, and are threaded into the other clamp ring, totighten the rings against each other, the inner and outer rings beingformed with a central recess of dove-tailed cross-section, in which aring-shaped metal disc is inserted having an outer surface substantiallymatching the dove-tailed conical surfaces of the inner and outer rings.The clamp ring against which the screw surfaces bear is additionallyformed with threaded openings to permit screws to be threaded therein,to then bear against the metal ring when separation of the hub to shaftconnection is desired.

1 1 Claims, 5 Drawing Figures PATENTEDJULM I972 in z y HUB-TO-SHAFTCLAMP CONNECTION ASSENIBLY The present invention relates to ahub-to-shaft clamping connection assembly, and more particularly to suchan assembly in which ring-shaped elements are inserted between the huband the shaft, formed with outwardly expanding, oppositely arrangedconical surfaces, to be together by clamping rings of substantiallysimilar conical surfaces, which are tightened together bycircumferentially arranged tightening screws.

Various interconnections from a hub to a shaft are known see for exampleGerman Pat. No. 1,099,806. Such interconnections in which a pair ofclamping rings, acting against each other on conical surfaces are used,have the advantages with respect to other clamping arrangements that,when the clamping arrangement is securely clamped for example bytightening nuts or screws, axial shifting of the clamping rings on theshaft, or in the hub, respectively, is avoided. Thus, the hub is exactlyplaced with respect to the shaft after tightening,

the shaft decreases frictional forces during tightening, so thatsubstantial torque can be transmitted. The angle of the generatrix ofthe cone usually is selected to be in the order of 14.2 minutes, whichcorresponds to a tangent of tan 0.25. The angle of the cone is thusabove that of self-binding, and the hub-to-shaft connection can bereleased. To provide for substantial transmission of torque between thehub and the shaft, a plurality of clamping screws are circumferentiallylocated, like planets in a planetary drive. The screws are made of highquality material, having a strength of lOO kp/mm A substantial axialclamping force can be obtained and the operative interconnection betweenshaft and hub, by means of the conical surfaces, provides good radialpressure. A large number of circumferentially arranged screws arenecessary, preferably so located that the heads of the screws are closeto each other. Such close location, requiring bores through one clampingring and threaded bores in the other have disadvantages, Among thedisadvantages are the expense of manufacture, and the time taken tomount such an assembly, particularly when the size of the hub-to-shaftconnection in creases. Approximately 44 clamping screws must betightened in order to secure a hub to a shaft having an average diameterof about 50 cm, the screws being standard metric M 24 type. As the shaftdiameter increases, the number of screws increases substantially. Thescrews additionally have to be tightened by means of a torque wrench, ina crossed tightening pattern, in order to be able to transmit the designtorque from shaft to hub. The transmitted torque thus depends to someextent on the accuracy and care with which the hub-to-shaft connectionis mounted or tightened by the mechanic carrying out the work.Reliability of operation depends essentially on the tightness and forceswith which the clamping screws are loaded.

It is an object of the present invention to provide a hub-toshaftconnection in which the connection can be separated without difficultyand in which the number of tightening screws to be used is decreased,while still being able to transmit, for equal dimensions, the same, orpreferably higher torque; and which are accurate with respect tocentricity of hub and shaft.

SUBJECT MATTER OF THE PRESENT INVENTION Briefly, inner and outer ringsare provided, the inner surrounding the shaft and the outer lyingagainst the inside of the hub. The rings are formed with opposingconical surfaces, diverging towards the outer sides. Interiorly of therings is a ring-shaped dove-tailed groove, providing an additional pairof conical surfaces, in which a ring-shaped metal disc is located havingouter surfaces matching the conical surfaces of the dove-tailed groove.The divergent conical surfaces of the inner and outer rings may have aconical angle, with respect to the central axis of the shaft, in theorder of 6, or less. Doubleconical clamp rings are inserted in the spaceformed by the divergent conical inner and outer rings, thedouble-conical rings being tightened against each other by clampingscrews passing through one ring, through the metal disc and beingthreaded into the other. The ring through which the screws pass isadditionally formed with at least one, and preferably a few morethreaded holes, so that, for removal, bolts can be inserted into thethreaded holes and tightened against the metal disc, to push out theclamping ring between the conical suras well as before. Avoidingshifting of the hub with respect to faces.

The screws preferably are Allen head screws made of a material having aminimum strength of kp/mm", thus being able to be stressed more and totransmit a higher torque.

The invention will be described by way of example with reference to theaccompanying drawings, wherein:

FIG. I is a longitudinal sectional view of a hub-to-shaft connection,utilizing split inner and outer rings, the section being taken alongline BB of FIG. 2;

FIG. 2 is a front view of the hub-to-shafl connection of FIG.

FIG. 3 is a fragmentary cross-sectional view, corresponding to the upperhalf of FIG. I, and illustrating a different embodiment;

FIG. 4 is a fragmentary cross-sectional view through the center line ofa shaft, illustrating a different embodiment; and

FIG. 5 is a fragmentary cross-sectional view through the center line ofthe shaft illustrating another embodiment, in which an axially splitmetal ring is used.

Referring now to the drawings and particularly to FIGS. 1 and 2: A slitinner ring I has outer conical surfaces lb, and is seated on a shaft 7.A hub 8 has an outer ring 2 located therein, likewise axially split (seeFIG. 2) and having inwardly facing conical surfaces 2b. The conicalsurfaces 1b, 2b face each other. The rings 1, 2 are formed at theircenter with a dove-tailed groove la, 20 respectively, in which a ring 3is located being formed with corresponding conical surfaces fitting intothe conical grooves Ia, 2a formed in the center of rings 1, 2. The rings1, 2, after having been assembled, form together with the ring 3 onecomplete non-removable unit, rings 1 and 2 being radially movable. Theassembly formed of rings 1, 2, and central ring 3 is connected togetherby clamping rings 4, 4a, which are inserted from both'sides betweenrings 1, 2. Clamping rings 4, 4a are interconnected by clamping screws6, having Allen heads. Screws 6 pass through bores formed in ring 4,through corresponding bores in ring 3, and are threaded into ring 4a.The screws hold the entire assembly together on the shaft and, whentightened, move the conical surfaces of rings 4, 4a towards each otherto press the rings 1, 2 away from each other and against the respectiveshaft, and hub elements.

Ring 4, through which the screws 6 pass is formed in addition to thebores through which the screws pass, with a pair additional bores 5(FIGS. 1, 2) which are threaded, the threading being preferably similarto the threads formed in ring 4a and receiving the bolts 6. The threadedholes 5, during operation, may be closed off by end or cap screws, forexample of plastic, and not shown.

When assembling the connection of FIGS. 1 and 2, tightening of bolts 6causes the concentrically located rings 1, 2 to be engaged by the rings4, 4a, which move against each other when bolts 6 are rotated, due tothe threads formed in the bores of rings 4a. The slit inner and outerrings 1, 2, which are separated by the metal ring 3, held in thedove-tailed grooves 10, 2a are elastically divided in two clampingparts, and are effectively radially evenly loaded with respect to shaft7 and against the bore of the hub 8, so that the torque transmittingconnection of the assembly between shaft 7 and shaft 8 becomeseffective, to transmit a substantial amount of torque. If theinterconnection is to be released, in spite of the small angle of theconical surfaces, which are self-binding, then bolts 6 are retractedfor; some distances and clamp ring 4a is freed from binding by lightimpacts, or hammer taps on the ends of bolts 6. Thereupon the closingscrews, previously inserted in holes 5 (if provided) are removed. Screws6 are screwed into the holes 5 until they bear against the metal ring 3.Continued rotation of screws 6 will now cause backing off ofthe clampring 4, thus releasing the clamping engagement of the ring 4 with theconical surfaces lb, 212 of the inner and outer rings, the entireconnection now being easily releasable.

Embodiment of FIG. 3: An axially slit inner ring 9, adapted to be seatedon a shaft, is faced, in spaced relation, by a similarly slit outer ring10, adapted to seat on the inside of the bore of a hub. Inner ring 9 hasdivergent conical surfaces 9a, the outer ring 10 is formed withdivergent conical surfaces 10a. The conical surfaces 9a of the innerring 9 have a smaller conical angle than the angle of the conicalsurfaces 10a of the outer ring. When the rings are loosely assembledwith clamp rings 12, 12a, and before being tightened, play indicated atx between the inner conical surfaces 100 of the outer ring 10, and theouter surfaces of the clamping rings 12, 12a will be present. The rings9, 10 are again formed longitudinally with a dove-tailed groove in whicha similarly profiled metal ring 11 is placed.

Upon axial stressing of the double-conical clamping rings I2, 120 byexerting pressure in the direction of the arrows, for example by thescrews as described in detail in connection with FIGS. 1 and 2 and notdescribed again, the conical inner ring 9 is first stressed. Thedouble-conical clamping rings 12, 12a then will be moved inwardly untilthe distance of the tolerance, or play .r is bridged so that the doubleconical clamping rings 12, 12a will engage the inner conical surfaces100 of the outer ring 10, to then provide pressure in radial directionagainst the outer ring 10. The radial pressures can thus so vary thatany shifting of the inner ring 9 on the shaft is effectively prevented,since the inner ring 9 is clamped before any clamping pressure isexerted against the outer ring I0.

Embodiment of FIG. 4: An axially slit inner ring I3 is faced with anaxially slit outer ring 14, rings l3, 14 having conical surfaces. Thefacing conical surfaces 130, 14a, of the inner and outer rings 13, 14,respectively, have different conical angles with respect to the facingconical surfaces 13b, 14b at the other side of the central metal ring16. The clamping rings 15, 15a have matching conical surfaces, that is,the conical surfaces of ring 15 matches those of surfaces 13a, 14a,whereas the surfaces of ring 150 matches the conical surfaces 13b, 14!).Of course, the surfaces of rings 13a, 1411 can be arranged to beslightly spaced, or slightly different, so that the play referred to inconnection with FIG. 3 is also obtainable in this embodiment. Axiallyextending clamping screws 6 pass through the clamping ring 15 and metalring 16, and are screwed into clamping ring 15a. The metal ring 16secures inner and outer rings 13, 14 together into one assembly. Theside having the conical surfaces with a flatter, or shallower conicalangle is preferably the side at the edge of the shaft 21 and hub 22, andalso the side from which the clamping screws 6 are introduced.

Embodiment of FIG. 5: The inner and outer rings in the embodiment ofFIG. 5 are not axially slit (as seen in FIG. 2) but rather are radiallyslit into two radially adjacent sections 18, 18a and 19, 19arespectively. The ring portions 18, 19 are formed with divergent conicalsurfaces, the ring portions 18a, 19a being formed with oppositelydiverging conical surfaces. Metal disc 17 likewise is formed of twoparts, which are interconnected by rivets, screws, spot welding or thelike after the ring sections 18, 18a and 19, 19a have been assembledthereover, so that the composite assembly formed of inner rings 18, 18a,circumferential ring 17, and outer rings 19, 190 forms an assembly ofwhich the parts are not readily separable. The surfaces of the ringsections forming the ring 17 match the conical surfaces of both theinner and outer rings, when assembled. Clamp rings 20, 20a, insertedfrom opposite sides in the assembly can then be stressed in direction ofthe arrows, for example by screws or bolts 6 (not shown in FIG. 5). Theconical surfaces on the ring portions 18, 18a and 19, 19a, respectively,may be as shown in FIG. 5 or have the relative relationships asindicated in FIGS. 3 or 4. Radially slitting the inner and outer ringsto form two ring sections 18, 18a and I9, 19a respectively permits useof completely circumferentially extending rings, assembled and heldtogether by the later joined portions of the circumferential ring 17;when the inner and outer rings are longitudinally slit, thecircumferential ring may be a single unit or single piece similar toring 3, although the conical surfaces and relationships illustrated inFIG. 5 can be maintained; thus, the groove holding the elements togetherneed not be formed in the inner and outer rings, but rather thedove-tailed groove can be in the circumferential ring 17, securing theinner and outer rings l8, 19 into one assembly, from which parts cannotbe readily separated, so that they might be lost.

The small conical angle of the clamping assembly of the presentinvention, for example having a tangent of tan 0.1 permits transfer of asubstantial amount of torque, much larger than that of other clampingarrangements which have a greater conical angle, for example of tan0.25. Additionally, centricity is improved and the clamping effectincreased even with comparatively small radial extent of thehub-to-shaft connection. Use of high strength clamping bolts 6, forexample of a material having a strength of I30 kp/mm further increasesthe torque transmission.

Various experiments and comparative measurements have been madecomparing the clamping effect of the hub-to-shaft connection of thepresent invention with known hub-to-shaft connections. On a shaft ofabout 50 mm diameter, to which a hub was connected of about mm diameter,12 screws were used with metric standard thread M 8, the screws having amaterial strength of I00 kp/mm A similar hub and shaft wereinterconnected with a hub-to-shaft connection of the present inventionutilizing only six screws of metric thread M 8, having a materialstrength of 130 kplmm The screws were tightened in accordance withmaximum tightening torque, in accordance with manufacturingspecification. The resulting axial clamping forces were surprising. Theprior art hub-toshaft clamp, utilizing the 12 clamping screws couldtransmit a maximum torque of M, 177 kpm. The hub-to-shaft connectionwith the same diameters, and using only six clamping screws of M 8 size,but having a material strength of I30 kp/mm could transmit thesubstantially higher torque of 250 kpm, thus effecting an increase intorque transmission of about I40 per cent. This substantial increaseappears to be due to the fact that the smaller conical angle of theclamping rings provides a greater transfer relationship, combined withthe increased strength of the holding screws or bolts. Still, theclamping connection could be separated without difiiculty since, eventhough the conical surfaces were self-binding, no

additional tools to release the clamp connection are necessary, to thepresence of threaded bores 5 (FIGS. 1, 2) permitting bolts to bethreaded therein and to release the outer clamping ring by pressureagainst the interior metal ring. Centricity of the connection wasfurther improved, and eccentricity reduced from 0.08 mm of knownclamping rings to 0.02 mm, with a connection tightened under shopconditions and loosely tightened. The dove-tailed interconnectionbetween the inner ring, the outer ring, and the interior metal ring,combined with the smaller conical angle of the clamping rings providesfor uniform radial pressure of the clamping rings between the shaft andthe bore of the hub, and thus effects essentially uniformcircumferential loading of all components. The interconnection of theinner and outer rings by the intermediate ring, to form one unitaryassembly from which parts cannot become lost or separated, is ofadvantage under shop conditions.

In the embodiment of FIG. 3, the play x may be so arranged that thespace x is parallel to the conical surfaces formed by the clamping rings12, 12a and by the outer ring 10. Thus, the space, in projection,indicated by the dimension x in FIG. 3 may be a parallel slit;alternatively, the angles of the conical surfaces and 10a may bedifferent, and, additionally, the angles of the conical surfaces 9a, or10a, and the engaging surfaces on the clamping rings 12, 12a may bedifferent. For example, the conical angle (with respect to an axialcenter line) 9a of the inner ring may be 3; the conical angle of theinner conical surfaces a of the outer ring 10 (with respect to a centralaxis of the hub, or shaft) may be 6. The cooperation of the differentangles of the cones of the inner and outer rings, in combination withthe play between the inner conical surface of the outer ring, and thecorresponding outer conical surface provides for transmission of maximumtorque, with reliable axial seating of the connection on a shaft.

The unit kp used in this specification means kilopond,

1 kp being equivalant to l kilogram force.

We claim:

1. Hub-to-shaft clamping connection assembly comprising an inner ring(1) adapted to seat on the shaft and having a pair of outwardly taperingconical surfaces (lb) and forming, with the center of the shaft, anangle up to about 6;

an outer ring (2) adapted to seat within the hub and having a pair ofoutwardly tapering conical surfaces (2b) spaced from the conicalsurfaces of the inner ring and forming with the center of the hub anangle of up to about 6;

a pair ofintermediate clamp rings (4, 4a) each having conical surfacesconcentric with the facing surfaces of the outer and inner ring, oneeach being insertable from a side of the connection to clamp the innerand outer rings against the shaft and hub, respectively, and the conicalsurfaces of the clamp rings against the conical surfaces of the innerand outer rings, respectively;

screw means (6) passing through one of the clamp rings and bearingagainst the outer face thereof, and threaded into the other clamp ringto tighten the clamp rings against each other, the inner and outerrings, each, being formed essentially at the center of the connectionassembly with dove-tail surfaces, to provide additional conicalsurfaces;

a metal ring (3) having an outer surface substantially matching theadditional conical surfaces, the metal ring (3) being formed withopenings matching the locking screw means to fasten the clamp ringstogether;

and wherein the clamp ring through which the screw means pass areadditionally formed with threaded openings (5) to permit threading ofthe screws therein to bear against said metal ring and thus permitrelease of said clamp ring after tightening.

2. Assembly according to claim 1, wherein the screw means have amaterial strength ofabout I30 kp/mm 3. Assembly according to claim 1,wherein the screw means are recessed head screws.

4. Assembly according to claim 1, wherein the outer conical surface (90)of the inner ring (9) has a lesser conical angle than the inner conicalsurface (10a) of the outer ring (10) to provide for play(x) between therespective surfaces of the clamp rings 12, 12a) before the assembly istightened.

5. Assembly according to claim 1, wherein the outer conical surface (9a)of the inner ring (9) and the engaging conical surface of the clamp ring(12, 12a) have conical centers to provide for engagement first of theconical surface of the inner ring and then, upon axial movement of theclamp ring, of engagement of the conical surface on the clamp ring withthe inwardly facing conical surface on the outer ring (10) to providefor first clamping pressure being exerted against the inner ring, andhence to seat the inner ring 9) on the shaft, before engagement ofclamping pressure against the outer ring (10) seating against the hub.

6. Assembly according to claim 1, wherein (FIG. 4) the conical angle atopposite outer and inner conical surfaces (13a, 14a) on one side of theinner and outer rings (l3, 14) respectively, are different from theconical angles of the outer and inner conical surfaces (13b, 14b) on theother side of the inner and outer rings, respectively; and the clamprings have conical surfaces engaging the differently angled conicalsurfaces of the inner and outer rings.

7. Assembly according to claim 6, wherein the additional conicalsurfaces are recesses formed in the inner and outer rings, of dove-tailcross-section, said additional conical surface bemg non-symmetrical withrespect to the axis of the connection assembly;

and the metal ring 16) has substantially matching non-symmetricalsurfaces.

8. Assembly according to claim 1, wherein the outer and inner rings andclosed rings (18, 18a, 19, 19a) divided centrally into ring portions;

and the metal ring (17) is formed of two parts with conical surfacesassembled together with said centrally separated rings, the end portionsof the conical surfaces projecting over the central portions of therings, the conical surfaces of the assembled metal ring holding theinner ring, the metal ring, and the outer ring together as a unitaryassembly.

9. Assembly according to claim 8, wherein the two parts of the ring areidentical as mirror images, the parts being secured together.

10 Assembly according to claim 1, wherein the inner and the outer ringare split rings.

11. Assembly according to claim 1, wherein the inner ring and the outerring, each, are formed with a recess (la, 20), said recess being ofdove-tailed cross-section and providing the additional conical surface,the metal ring being seated within said recess and having essentiallymatching conical surfaces.

1. Hub-to-shaft clamPing connection assembly comprising an inner ring(1) adapted to seat on the shaft and having a pair of outwardly taperingconical surfaces (1b) and forming, with the center of the shaft, anangle up to about 6*; an outer ring (2) adapted to seat within the huband having a pair of outwardly tapering conical surfaces (2b) spacedfrom the conical surfaces of the inner ring and forming with the centerof the hub an angle of up to about 6*; a pair of intermediate clamprings (4, 4a) each having conical surfaces concentric with the facingsurfaces of the outer and inner ring, one each being insertable from aside of the connection to clamp the inner and outer rings against theshaft and hub, respectively, and the conical surfaces of the clamp ringsagainst the conical surfaces of the inner and outer rings, respectively;screw means (6) passing through one of the clamp rings and bearingagainst the outer face thereof, and threaded into the other clamp ringto tighten the clamp rings against each other, the inner and outerrings, each, being formed essentially at the center of the connectionassembly with dove-tail surfaces, to provide additional conicalsurfaces; a metal ring (3) having an outer surface substantiallymatching the additional conical surfaces, the metal ring (3) beingformed with openings matching the locking screw means to fasten theclamp rings together; and wherein the clamp ring through which the screwmeans pass are additionally formed with threaded openings (5) to permitthreading of the screws therein to bear against said metal ring and thuspermit release of said clamp ring after tightening.
 2. Assemblyaccording to claim 1, wherein the screw means have a material strengthof about 130 kp/mm2.
 3. Assembly according to claim 1, wherein the screwmeans are recessed head screws.
 4. Assembly according to claim 1,wherein the outer conical surface (9a) of the inner ring (9) has alesser conical angle than the inner conical surface (10a) of the outerring (10) to provide for play(x) between the respective surfaces of theclamp rings (12, 12a) before the assembly is tightened.
 5. Assemblyaccording to claim 1, wherein the outer conical surface (9a) of theinner ring (9) and the engaging conical surface of the clamp ring (12,12a) have conical centers to provide for engagement first of the conicalsurface of the inner ring and then, upon axial movement of the clampring, of engagement of the conical surface on the clamp ring with theinwardly facing conical surface on the outer ring (10) to provide forfirst clamping pressure being exerted against the inner ring, and henceto seat the inner ring (9) on the shaft, before engagement of clampingpressure against the outer ring (10) seating against the hub. 6.Assembly according to claim 1, wherein (FIG. 4) the conical angle atopposite outer and inner conical surfaces (13a, 14a) on one side of theinner and outer rings (13, 14) respectively, are different from theconical angles of the outer and inner conical surfaces (13b, 14b) on theother side of the inner and outer rings, respectively; and the clamprings have conical surfaces engaging the differently angled conicalsurfaces of the inner and outer rings.
 7. Assembly according to claim 6,wherein the additional conical surfaces are recesses formed in the innerand outer rings, of dove-tail cross-section, said additional conicalsurface being non-symmetrical with respect to the axis of the connectionassembly; and the metal ring (16) has substantially matchingnon-symmetrical surfaces.
 8. Assembly according to claim 1, wherein theouter and inner rings and closed rings (18, 18a, 19, 19a) dividedcentrally into ring portions; and the metal ring (17) is formed of twoparts with conical surfaces assembled together with said centrallyseparated rings, the end portions of the conical surfaces projectingover the central portions of the rings, the conical surfaces of theassembled metal ring holding the inner ring, the metal ring, and theouter ring together as a unitary assembly.
 9. Assembly according toclaim 8, wherein the two parts of the ring are identical as mirrorimages, the parts being secured together.
 10. Assembly according toclaim 1, wherein the inner and the outer ring are split rings. 11.Assembly according to claim 1, wherein the inner ring and the outerring, each, are formed with a recess (1a, 2a), said recess being ofdove-tailed cross-section and providing the additional conical surface,the metal ring being seated within said recess and having essentiallymatching conical surfaces.